1. Field of the Invention
This invention deals generally with the use of CBr.sub.4 as a reactive atmosphere processing (RAP) agent for the growth of metal bromides and more particularly to the generation of nascent Br during the pyrolytic dissociation of CBr.sub.4.
2. Description of the Prior Art
The closest known prior art related to the use of carbon tetrabromide in the growth of metal halide crystals is contained in an article entitled "Crystal Growth of KBr in a Reactive Atmosphere" published in the Materials Research Bulletin, Vol. 10, pp. 261-266, (1975) of the Pergamon Press by Applicants herein and M. A. Aaronson where the problem solved by the present invention is identified.
Applicants also defined the problem solved by this invention in "Crystal Growth in a Reactive Atmosphere" published at pp. 117-124 of the Materials Research Bulletin, Vol. 10, referred to above.
Applicants herein further discussed the problem associated with the pyrolysis of CBr.sub.4 in their U.S. Pat. No. 4,076,574, issued Feb. 28, 1978.
In each of the above-identified processes, the use of CBr.sub.4 as a nascent halogen source in a RAP crystal growth process is taught to be precluded by the nature of the dissociation path taken above certain temperatures when CBr.sub.4 is utilized as a source of nascent bromine. It was shown that for congruent growth of KBr from the melt the desired dissociation path EQU CBr.sub.4 .fwdarw.CBr.sub.3 +Br (1)
gives way to the competing path: EQU CBr.sub.4 .fwdarw.C+2Br.sub.2 ( 2)
which yields undesirable results during crystal growth processes.
Ultra pure large single crystals of alkali metal bromides and alkaline earth metal bromides may be produced by crystal growth from the melt processes which utilize a reactive atmosphere comprised of nascent bromine. Nascent bromine has been found to be a substantially superior gettering agent for anion impurities than other gettering agents such as molecular bromine.